This invention relates to an apparatus and method for interconnecting an artery and vein, and more particularly to providing, through such an interconnection, an artificial access to a patient""s bloodstream for hemodialysis.
The United States Renal Data System has estimated the number of patients with end-stage renal disease (ESRD) in 1989, including those with functioning kidney transplants, to be greater than 200,000. Since the inception of hemodialysis for end-stage renal disease, various types of arterio-venous (AV) conduits have been provided to provide access to the bloodstream. Various access options have been used, including external arterio-venous shunts, native arterio-venous fistulas, and various arterio-venous grafts (AVG) such as reverse saphenous vein, bovine heterograft, DACRON, and expanded polytetraflouroethylene (ePTFE). The grafts function as artificial vessels into which needles can be repeatedly inserted (such as about three times per week) to allow blood to be removed from a patient""s bloodstream, and to allow the blood to be returned to the patient""s bloodstream after it has passed through a hemodialysis machine. These grafts typically have one end connected to an incision on the wall of an artery and another end connected to an incision on the wall of a vein.
In certain hemodialysis patients, autogenous fistulas cannot be constructed. PTFE is a graft material of choice for such patients.
Thus, arterio-venous grafts, as opposed to creation of fistulas, are used in a substantial portion of the end-stage renal disease population, although this portion of the population varies from country to country.
Many arterio-venous grafts (AVGs) have patency rates of about two years. Thrombotic complications associated with such grafts contribute to hospital admissions for end-stage renal disease patients.
The patency of arterio-venous grafts can be maintained or re-established by interventions including lytic therapy, angioplasty, stenting, mechanical thrombectomy, and operative revision. Of course, there are costs associated with these interventions.
Outflow obstruction caused by intimal hyperplasia at the graft-venous connection (anastomosis) can cause arterio-venous grafts to fail. The above-listed interventions can be used as sub-optimal remedies for intimal hyperplasia, at some cost.
The invention provides apparatus and methods for interconnecting an artery and a vein. The apparatus includes a graft of biocompatible material and a catheter of biocompatible material. The graft has an end configured for attachment to the artery and another end configured for interconnection with the catheter. The catheter has an end configured for interconnection with the graft and has at least one hole spaced axially therefrom that is positionable within the interior of the vein and spaced from an opening of the vein through which the catheter passes into the vein. The at least one hole provides an outlet within the interior of the vein for blood from the artery that passes through the graft and the catheter.
The invention has the potential to decrease substantially the arterio-venous graft (AVG) failure rate due to venous outflow tract stenosis in end-stage renal disease (ESRD) hemodialysis patients. In particular, the invention can potentially reduce arterio-venous graft failure resulting from venous outflow tract stenosis. This result is accomplished by avoiding a graft-to-vein sutured connection (anastomosis) and instead employing a catheter introduced into the interior of the vein through a small puncture hole on the wall of the vein.
It is believed that venous outflow obstruction secondary to myointimal hyperplasia may be caused by 1) high-flow turbulent blood passing through the graft-to-vein sutured connection (anastomosis) 2) trauma to the vein wall incurred by the suturing and surgical handling of the vein and 3) compliance mismatch between a relatively thick and rigid ePTFE graft and a thin elastic vein.
The present invention avoids the above-listed factors by 1) distributing the high blood flow over a longer segment of vein through side holes on the catheter; 2) limiting vein wall trauma to a single puncture hole and 3) ensuring that the catheter sits on the interior of the vein, thereby avoiding compliance mismatch problems.
Due to the reduction of venous outflow obstruction, it is anticipated that the invention can improve patency rates and lead to substantial reduction in hospital admissions and the cost of interventions such as lytic therapy, angioplasty, stenting, mechanical thrombectomies, and operative revisions. As a result, it is expected that the invention can markedly reduce morbidity, mortality, and cost among end-stage renal disease patents.
The catheter and graft of the present invention may be provided as a combined assembly, or, in a modification of the invention, the catheter may be inserted through the wall of an existing graft in order to salvage the existing graft. When an existing arterio-venous graft (AVG) is failing due to venous outflow obstruction, the modified invention can salvage the graft. In particular, one specific implementation of the invention for salvaging of the graft is as follows: the graft is percutaneously cannulated by conventional means and the graft-to-venous connection (anastomosis) is angioplastied. Via the existing sheath and guide wire used for the angioplasty a catheter that is funnel-shaped on one end and has side holes on the other end is inserted through the graft-to-vein connection (anastomosis). The funnel-shaped part of the catheter lies in the pre-existing graft and the slim end (tail) lies in the interior of the vein. The resulting modified assembly accomplishes complete bypass (exclusion) of the graft-to-vein connection (anastomosis), and any subsequent myointimal restenosis should not affect venous outflow.
Numerous other features, objects, and advantages of the invention will become apparent from the following detailed description when read in connection with the accompanying drawings.